Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles.
Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles.
复制标题
DOI：
10.1039/c3nr00917c
复制
发表时间：
2013-06
期刊：
影响因子：
6.7
通讯作者：
T. Sayle;M. Molinari;Soumen Das;U. Bhatta;G. Möbus;S. C. Parker;S. Seal;D. Sayle
中科院分区：
文献类型：
--
作者：
T. Sayle;M. Molinari;Soumen Das;U. Bhatta;G. Möbus;S. C. Parker;S. Seal;D. Sayle
纳米材料具有作为生物药剂的潜在应用，利用固体的化学性质，具有被运输（像分子一样）到各种身体隔室的能力。然而，化学环境可以显著改变纳米材料的结构和性质。因此，其表面反应性严重依赖于其所处的（生物）环境的性质。在这里，我们使用分子动力学（MD）模拟，密度泛函理论（DFT）和畸变校正TEM预测和合理化的结构差异，因此在不同的环境中的氧化铈纳米粒子的表面反应性。特别是，我们计算的反应性'指纹'的未还原和还原的二氧化铈纳米粒子浸泡在水中和真空中。我们的模拟预测较高的活动的二氧化铈纳米粒子，对氧气的释放，当浸入水中，因为水淬灭表面离子的配位不饱和。相反，在真空中，表面离子弛豫到纳米颗粒的主体中以减轻配位不饱和，这增加了与氧释放相关的能垒。我们的模拟还表明，还原的二氧化铈纳米颗粒对表面氧释放更活跃相比，未还原的纳米二氧化铈。同时，通过实验研究了氧化铈纳米颗粒在环境变化后的活性。特别是，我们比较了氧化铈纳米粒子的能力，在水性环境中，与相同批次的纳米粒子相比，它已经首先干燥，然后再水化，以消除超氧自由基。后者显示出明显的活性降低，这与不同环境之间移动相关的氧化还原化学变化有关。因此，二氧化铈纳米颗粒的反应性不仅是环境依赖性的，而且还受到到达其反应性将被利用的特定环境所需的运输途径或历史的影响。
Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity 'fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular environment in which its reactivity is to be exploited.